In June 2015, Michigan became the 21st state to enact breast density notification legislation. This requires that mammogram facilities inform patients if they have dense breast tissue on mammography. This will be done in the form of a letter. At MidMichigan Health, we include this in the result letter that we send out for every mammography patient. It is also included in the radiology report that is sent to your health care provider.
What is breast density?
Breasts are made up of a mixture of fibrous and glandular tissue as well as fat. Fibrous and glandular tissue are displayed as white on a mammogram. Fat shows up as black. Some women have denser breast tissue than others; this is not completely understood. In some women, breast density may decrease with age. Having dense breasts is not abnormal – 50 percent of women have dense breasts.
Breast density is separated into four categories, determined by the radiologist interpreting your mammogram. The image at the right shows an image of what these are and their assigned categories (almost entirely fat (a), scattered fibroglandular densities (b), heterogeneously dense (c) and extremely dense (d)).
The image to the left shows a distribution of breast density for women in the United States. Ten percent of women have almost entirely fatty breasts and 10 percent have extremely dense breasts. Eighty percent are classed in one of the middle two categories.
Why is this important?
Studies have shown that dense breasts may increase the risk of developing a breast cancer. Also, masses, which can be benign or malignant, show up as white on a mammogram. Therefore, the dense tissue may obscure a small mass.
Screening mammography is still the only medical imaging screening test proven to reduce breast cancer deaths. Many cancers are seen on a mammogram even in patients with dense breast tissue. However, studies have shown that small cancers can be detected with additional supplemental exams such as with ultrasound or MRI, which cannot be seen on a mammogram. Both MRI and ultrasound show more findings that are not cancer, which may lead to additional testing and unnecessary biopsies. Also, the cost of these studies may not be covered by insurance. In my experience, ultrasound is the more frequently covered exam, but I encourage you to check with your individual health insurance provider for specific details.
If you do not have dense breasts, the recommendation is for a screening mammogram on an annual basis starting at the age of 40. Not having dense breasts should not provide a false sense of security or mean that you will not develop a breast cancer or do not need screening. Other factors may still place you at increased risk for breast cancer, including but not limited to a family history of the disease, previous breast biopsies and previous chest radiation.
If you do have dense breasts and are thinking of having additional screening studies, please talk to your health care provider. You can decide together which, if any, additional screening exams are right for you.
MidMichigan Health offers screening breast ultrasound and breast MRI in addition to a screening mammogram. Ultrasound and MRI are not intended to replace the annual mammogram. Increased sensitivity in breast cancer detection has only been proven in use with a current mammogram. As I said previously, many cancers are still visible on mammograms even in patients with dense breast tissue.
For more information on breast density and breast cancer screening, visit www.midensebreasts.org or www.mammographysaveslives.org.
To schedule a screening mammogram, breast ultrasound or breast MRI, contact MidMichigan -Health at (888) 367-2778.
Lindsay Zeeb, M.D., board-certified diagnostic radiologist, is the medical director of Breast Imaging and the Center for Women’s Health at MidMichigan Medical Center – Midland. As a breast imaging specialist, Dr. Zeeb reads and interprets the images produced by mammography, ultrasound and magnetic resonance imaging (MRI), then makes recommendations for further diagnostic testing and treatment. She also conducts image-guided breast biopsies. She believes that patients play a pivotal role in the battle against breast cancer and that keeping up with yearly mammograms can help diagnose cancer early, when it is most curable.